In many countries soldiers serving in specific occupations are referred to by terms other than their occupational name. For example, military police personnel in the British Army are known as "red caps" because of the colour of their caps (and berets).

Infantry are sometimes called "grunts" (in the United States Army) or "squaddies" (in the British Army), while U.S. Army artillery crews, or "gunners," are sometimes referred to as "redlegs", from the service branch color for artillery.[citation needed] U.S. soldiers are often called "G.I.s" (short for the term "General Issue").

French Marine Infantry are called marsouins (French: porpoises) because of their amphibious role.[citation needed] Military units in most armies have nicknames of this type, arising either from items of distinctive uniform, some historical connotation or rivalry between branches or regiments.

Some soldiers, such as conscripts or draftees, serve a single limited term. Others choose to serve until retirement; then they receive a pension and other benefits. In the United States, military members can retire after 20 years.[3] In other countries, the term of service is 30 years, hence the term "30-year man".